1. Field of the Art
Embodiments of the present invention generally relate to biomedical membranes and, in particular, to ultrathin (e.g., between 0.01 μm to 5 μm thick) parylene C membranes that have exhibited permeability that is ideal for monolayer biological cell growth.
2. Description of the Related Art
Biological cells are often grown on membranes. For optimal growth of on on-membrane cell culture, the membranes must be permeable to nutrients (and waste from cells), such as proteins in serum. Membranes with pores that are large enough to allow proteins to flow through are used extensively in laboratories and are finding new applications as analysis equipment becomes smaller and more efficient.
Porous membranes are widely used in Micro Total Analysis System (gTAS) and Lab-on-a-Chip (LOC) applications, allowing chemical or biological reagents transportations and filtration. Among different types of membranes, commercially available track-etched porous membranes are one of the most popular choices, with various sizes of holes in submicron and micron (μm) ranges. Track etching involves heavy-ion bombardment of thin films and then chemical etching to reveal the tracks into holes.
Parylene, a generic name for members of a series of polyp-xylylene) polymers, is generally biocompatible. Of the common types of parylene, parylene C is perhaps the most widely used in industry. Parylene C is sometimes referred to with a dash, i.e., “parylene-C,” and sometimes is abbreviated as “PA-C.” Its demonstrated bio-compatibility as a United States Pharmacopeial Convention (USP) Class VI biocompatible polymer makes it suitable for medical devices. However, it is not porous or considered permeable. In fact, it is used extensively in industry as a conformal coating for electronics and medical devices because it is water tight and essentially pinhole-free when chemical vapor deposited in extremely thin layers.